Should I care about topology after applying booleans?
If the object isn't going to be animated and the topology doesn't cause any problems elsewhere (e.g. because hard edges are used and bad topology becomes apparent), then you don't have to. 

If you'd like to retopo a static object, but don't like to spend a lot of time on it, I'd suggest taking a look at Instant Meshes an open-source tool for automatic retopo operations.